New Delhi, Sept. 25 -- The global boom in GLP-1 medicines is facing a fresh safety question as regulators, researchers and US courts examine a possible link between semaglutide and non-arteritic anterior ischaemic optic neuropathy (NAION), a rare condition that can cause sudden vision loss.

The issue gained renewed attention after Novo Nordisk cited clinical-trial data showing a small number of confirmed NAION cases among people taking its GLP-1 medicines. At the same time, several studies using real-world patient data have reported an association between semaglutide and NAION. European regulators have classified the condition as a very rare side effect of semaglutide.

NAION occurs when blood flow to the optic nerve is disrupted, genera...